2K Marin is developing XCOM, not the 2K Marin.
According to 1UP, the Australian arm of 2K Marin is the house where the new XCOM title is being built, which is not the same house we would attribute as the main driver behind BioShock 2. That one is in Novato, California.
The two are “sister studios,” as explained by a rep speaking with 1UP, and as such, 2K Games simply just rolled with their shared studio name in the press release announcing the revival of the classic IP. But there’s no need to feel burned. These guys apparently did their share of work in BioShock 2 and have been around for a bit. We’re excited to see what they’ve got, and even more excited to see XCOM again.
Core BioShock 2 Team Not Leading XCOM Development [1UP]